1. Field of the Invention
The present invention relates to a solid-state image pickup device.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2002-33469 describes a back surface incident type of solid-state image pickup device. In the solid-state image pickup device, light incident on the back surface of a semiconductor substrate from an object is photoelectrically converted inside the semiconductor substrate. Electric charges produced by the conversion are received by a light receiving unit to image the object.
Japanese Patent Laid-Open No. 2000-217803 in addition to Japanese Patent Laid-Open No. 2002-33469 is known as a prior art document related to the present invention.
The present inventor has recognized as follows. The solid-state image pickup device described in Japanese Patent Laid-Open No. 2002-33469 leaves room for improvement in terms of easy release of excess charges. In this respect, the resistivity of the whole substrate needs to be reduced to easily release excess charges. This, however, makes it difficult to directly use a platform in an existing device process without modification when a light receiving unit is formed in the substrate.